It has been a general objective in the field of biotechnology to develop gene therapy protocols in order to cure and/or treat diseases and illnesses which are at least partially caused by genetic disorders or may be treated with gene therapy protocols. For example, there exists a gene therapy protocol for the correction of adenosine deaminase (ADA) deficiency. See W. French Anderson, Science, volume 256, pages 808-813 (May 8, 1992). Many procedures for gene therapy must deal with the issue of delivering the new genetic material ("gene") into the target cells which are delivered into the organism for which gene therapy is to be carried out.
In the prior art, there are numerous methods for causing this delivery, such as the use of liposomes, microinjection, infectious viral vectors, and calcium phosphate mediated DNA transfer. The use of liposomes, while somewhat popular, requires a considerable effort in designing a liposome carrier for genetic material and is often not efficient in effecting a transfer of genetic material any may often clot lung capillary vessels. Microinjection is a very tedious and slow process given that each cell must be injected while observing the cell in a light microscope. The predominant approach currently for causing the transfer of new genetic material into the recipient cells for delivery into the organism for which gene therapy is intended has been the use of viral vectors which are designed to infect and transform a target cell from the organism, which target cell, after transformation, is placed back into the organism typically by implantation into the organism or injection into a circulatory system of the organism.
While most of gene therapy under investigation today, particularly gene therapy for use in humans, involves the use of somatic cells as the target cell, gene therapy has been considered for use in germ cells and in stem cells, such as hematopoietic stem cells, as the target cell. The selection of a particular viral vector will depend on the particular target cell and thus there is considerable specificity required in determining the viral vector relative to the particular target cell. That is, the selection of the viral vector will depend on the selection of the target cell and there are no general or simple rules in the case of selecting viral vectors for use with particular target cells for use in gene therapy. Thus, research is continuing on various improved methods for delivering genetic material into target cells for use in gene therapy.
One technique in the prior art for delivery of genetic material into cells has been the use of electronic pulse delivery systems and procedures such as those described in U.S. Pat. No. 4,849,355 and U.S. Pat. No. 4,663,292. While these procedures and techniques have been utilized to transfer macromolecules into cells, they have not been used for the purpose of gene therapy. The prior art electronic pulse delivery systems utilized reaction chambers with pointed electrodes in order to maximize the electric field near the electrodes and utilized reaction chambers where at least one electrode was in contact with the solution containing the cells. This has been found to not be as advantageous as certain improved reaction chambers, provided by the present invention, with substantially flat electrodes and where the electrodes are physically isolated (and electrically insulated) from the solution containing the cells.
Thus, it is desirable to provide an improved technique for delivery of genetic material into cells for the purpose of performing gene therapy treatment on the organism, typically by placing transformed cells back into the organism.